A 20-pound (9-kg) Asian carp was fished out of a waterway close to the Great Lakes and beyond twin electric barriers designed to keep them out, authorities said on Wednesday.

It was the first time the voracious invader has been found beyond the electric barriers in the waterways that connect Lake Michigan, one of the five Great Lakes, with the Mississippi River basin, where the carp have proliferated.

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"It's important evidence, and the more information we know about where the carp are, the better ... that's the reason we're intensifying the effort" to find any Asian carp beyond the barriers, said Chris McCloud, a spokesman for the Illinois Department of Natural Resources.

The live Bighead carp was fished out on Tuesday by a fisherman contracted by the government in Lake Calumet, 6 miles from Lake Michigan. It could have been dumped there or could have found its way past the electric barriers meant to block all fish species, McCloud said.

Michigan and several other U.S. states bordering the Great Lakes have filed suit demanding a separation of the two basins, fearing Asian carp will ruin the Great Lakes' $7 billion fishery. Several environmental groups support the separation of the basins, which were connected by man-made waterways a century ago.

Commercial interests including tour boat operators, barge companies, and the recreational boating industry oppose the closing of the connecting waterways.